Grinding apparatus



J. c; CURTIS GRINDING APPARATUS 3 Sheets-Sheet 1 Filed Dec. 30, 1942 JoZzzz 66242-223.

A I'M Aug. 31, 1948. v .1. c. CURTIS GRINDING APPARATUS 3 Sheets-Sheet 2' Filed Dec. 30, 1942 aw wt 36 Patented Aug. 31, 1948 GRINDING APPARATUS John 0. Curtis, Claremoni' N. 11., assignor to Joy Manufacturing Comp Pennsylvania any, a corporation of Application December 30, 1942, Serial No. 470,688

This invention relates to grinding apparatus, and more particularly, but not exclusively, to improved apparatus for grinding detachable rock drill bits in order to determine the proper bit gauge. 7

Many rock drill bits are of the so-called double-taper type, having the rearward portions of their bodies bounded by a frusto-conical surface the elements of which make an angle of about 14 with the axis of the bit; and the forward portions of these bits have their lateral surfaces also in coincidence with frusto-conical surf-aces, these latter frusto-conical surfaces having their elements at an angle of about with the bit axis. The latter portions of these bits determine the gauge. During the bit grinding operation, in certain known forms of grinding apparatus, the drillbit was usually rapidly rotated about its axis as it was moved toward and from the grinding wheel periphery, while maintained with its axis of rotation substantially at an angle of 5 to the .axis of rotation of the grinding wheel. By contacting the drill bit with the grinding wheel in such a manner, it was found that wheel Wear was excessive and uneven, so'that frequent dressing of the wheel was necessary. This resulted in decreased life of the wheel and increased cost of grinding.

It is an object of the present invention to provide an improved bit grinding apparatus for overcoming the disadvantages of previously known apparatus. Another object is to provide animproved bit grinding apparatus in which the bit is guided for movement in a rectilinear path, tangential with respect to the grinding wheel periphery, so that the grinding wheel is evenly worn away, substantially reducing .the necessity of dressing the wheel. A further object is to provide improved means for supporting and guiding a drill bit during its movement with respect to the grinding wheel. Yet another-object is to provide improved means for rapidly rotating the drill bit as it is movedi'n a rectillnearpath'tangent-ially with respect to the grindingwheel. A still further object is to provide improved means for supportingthe drill bit for adjustment into difierent ang=ularlyrelated positions with respect to the grinding wheel. Still another object .is to provide an improved bit grinding apparatus em bodying means for effecting feedingmovement of the drill bit in a rectilinear path tangentially with respect to thegrinding wheel.- Yet another object is to provide improved supporting and guiding means forthe drill bit for guiding the 9 Claims. (01. 51-95) respect to thegrinding wheel while the axis of the .drill bit ismain-tained at right angles to the axis of rotation of the grinding wheel. These and other objects and advantages of the inventionwill, however, hereinafter more fully appear.

In theaccompanying drawings there is shown for purposes of, illustration one form which the invention may assume in practice.

In these drawings:

Fig. 1 is a plan view of a bit grinding apparatus constructed in accordance with an illustrative embodiment of the invention.

Fig. 2 is an elevatlonal view, partially shown in section, of the grinding apparatus shown in Fig. 1., Y

Fig. 3 isaview partially in vertical section and partially in elevation showing a drill bit in operative position on the Work holder shaft.

... .".i .4 is av vertical sectional view taken substantially on line 4-4 of Fig. 1.

Fig. 5 is a vertical section-a1 viewtaken substantially on line 5-5 of Fig. 1. 5

Fig. 6 is an enlarged detail sectional view take substantially on line 6--6 of Fig. 2. v

Fig. 7 is an enlarged detail sectional view taken substantially on line 1-1 of Fig. 4, with parts in plan, s

Fig. 8 is a view similar to Fig. 4, with parts shown in full and with the work holder in an inclined position.

Fig.. 9 is a fragmentary view similar to Fig. 2, showing the work holder in its raised position with respect to the grinding wheel.

Fig. 10 is 'an [enlarged detail sectional view taken. substantially on line Ill-40 of Fig. 2.

Figrll is a somewhat schematic view, showing drill bits of different diameters in grinding relation, with the grinding wheel.

Injthis illustrative embodiment of the invention there is shown a conventional grinding wheel I, and improved supporting and guiding means, generally'designated 2, for a work piece 3.

The work piece 3 is herein in the form of a detachable 'roc'k ann bit which may be of a type similar to that shown in the patent to one PaulH. Nast, No. 2,168,102, patented August 1, 1939. 'As illustrated, the drill bit comprises a body 4 provided with a threaded socket 5 and adapted for' attachment to the .threaded end of a conventional drill rod or steel in the manner well known to those skilled in the art. The bit bodyhas pairs of wings 6, 6 and I, 1, the former having alined cutting edges 8 lying in a. diametric line and the latter having arcuate chopping edges latterin a rectilinear. pathftangentially with 5 9 ly ng at the outer periphery of the bit. The

these degrees of taper may vary considerably in 5 different size bits. It is to the grinding of the forward, frusto-conical surface H, in order to determine the proper bit gauge, that thepresent invention relates.

The improved grinding apparatus comprises a bed frame or base M on which is carried amotor I5, to the power shaft of which the grinding wheel I is secured, so that the motor may rapidly rotate the grinding wheel. There are parallel horizontal guides I5 attached to the end portions of a bracket ll secured to the'bed frame, and a horizontal frame [8 is slidably guided on these parallel guides. Carried by the sliding frame 18 aresubstantially vertical guides l9 rigidly connected at their upper ends by a cross plate '20. The guides l5 and I9 comprise tie-bolts passing through spacing sleeves, and the ends of the sleeves may be seated in appropriately spaced bores in the parts by whichthey are supported, in order to maintain the guides in proper spaced relation. A crosshead-2| -is slidably guided-for vertical movement along the vertical guides. A hand lever "22 is pivoted at 23 on the bed frame and is pivotally connected at 24 as by a pin and slot to a lug 25 integral with the frame I8, for sliding the latter back and forth along the horizontal guides. For moving the crosshead 2| along the vertical guides thereis provided a-chain sprocket 26 arranged between the guides and fixed to a horizontal shaft 2-1 journaled in suitable openings in the vertical guidesneartheir lower ends, and fixed to the shaft 21 is a'hand wheel 28. The sprocket 26 engages a chain 29 which is guidedat its upperportion by a-guide sprocket 55 fixed to a horizontal shaft 3|, suitably journaled in openings in the vertical guides near their upper ends. This chain is attached at its ends at 32 to the crosshead, so that' when the sprocket 26 is rotated by the hand wheel, the chain-is circulated relative to its guides to'move the crosshead either upwardly or downwardly along the vertical guides. Attached at one end at 33 to the crosshead isa chain 34 which passes around a guide sprocket 35 suitably journaled on the shaft 3|. The chain 34'also'passes around a guide sprocket 36 journaled on a horizontal shaft 31 at the upper end "ofastandard 38'mounted on the bed frame. The other end of the chain 54 is attached at 39 to'a counterweight 40 which, to a large extent, counterbalances the weight to the crosshead so that manual feeding of the latter, together with the parts supported thereby, upwardly along theguides is facilitated. A suitable-stop 4| is provided for limiting downward movement of the crosshead along the vertical guides.

In accordance with this invention, swiveled at 42 on a horizontal axis on a vertical plate 43 secured to the crosshead 2|, is a vertical work supporting plate 44. Screws fl5 secured to the plate 43 andpassing through arcuate slotsin the swivel plate 44, limit the extent of swinging movement of the swivel plate. 'By tightening these screws the swivel plate may be firmly secured in adjusted position. Projecting laterally from the swivel plate is a substantially horizontal arm 46 which carries a support 41 for a motor 48. Fixed to the upright motor power shaft is a spur pinion 49 meshing with a spur gear 50 journaled on a vertical shaft 5| mounted on the support 41'. Also journaled on the shaft 5| and secured tothe gear is a pulley 52 connected by an endless'drive belt 53 to a pulley 54 connectible to an upright work holder shaft 55. The shaft 5| passes through an arcuate slot 55 on thesupport 45 (Fig. '7), and the lower end of the shaft is threaded to receive a tightening nut 51. Whenthe' nut 51 'isloosened the shaft 5| may be movedin'the arcuate slot 56, moving the pulley 52 horizontally about an axis coincident with the axis ofthe power shaft of the motor 48, thereby to vary the tension 'of the drive belt 53 in an obvious manner. When the drive belt is properly tensioned, the nut 51 may be tightened to hold securely the parts in adjusted position. The work. holder shaft 55 extends through a bore 58 ofa barrel 5E1 integral with the swivel plate 44, and the shaft 55 is suitably journaled in bearings supported within the barrel. The pulley 54 is connectible to the shaft 55 by means of a friction clutch Iii) including a cone clutch element 6| fixed tothe shaft and a cooperating clutch 62 integral with the pulley. A coil spring 63 surrounds the shaft'55 between the upper head of the barrel 59 and the lower surface of the pulley for urging the clutch elements yieldingly into frictional engagement. Other known types of friction clutches may be used in place of that shown, if desired.

In this instance, journaled on a depending bracket 64 carried by the cross plate 20 at the upper ends of the vertical guides is aroller 65, and when the crosshead 2| is fed upwardly along the vertical guides the upper surface of the pulley 54 engages the rollerand-moves into the position shown in Fig. 9 to release the upper clutch element 5| from the clutch element 62 to effect interruption of the drive between the motor and work holder shaft. Thus it will be seen that when the work holder reaches its limit of travel along the vertical guides, the drive of the holder shaft is automatically interrupted. 'When the crosshead'2l is again lowered, the clutch is automatically applied by the coil spring. As previously mentioned, by loosening the screws 45 and adjusting the swivel plate 44 on its swivel axis, the angularrelation .of the work holder with respect to the grinding wheel may be varied. The release roller 65 is so arranged that in all normal positions of adjustment of the swivel plate on its swivel axis, theclutch is released when the work holder reaches its limit of upward travel.

As shown in Fig. 3, the work holder shaft55 is threaded at 56 at its lower end, andthe detachable drill bit'3 is adapted to .be threadedonto the shaft with the threaded socket S5 of thebit receiving the threaded endof the shaft. It will be evident that: the bit mayibe attached to the work holder shaft in various manners and that drill bits of differentdiameters, as indicated ;at hand B in Fig. 11, may be attached to the shaft.

The mode of operation .of the improved grinding apparatus will be .clearly apparentfrom the description given, Upon "starting of the'motor 15 th grinding wheel is rapidly rotated. The angular. position of the work piece with. respect to the periphery of'the grinding 'wheelmaybe adjusted simply by loosening the screws. and swivelling the plate 44 into the desired relation.

The work holder may be swung fromthe vertical position shown inEig. 4 withthe axis of the work holder shaft perpendicular to the axi of rotation of the grinding -,wheel, to'the inclined position shown in Fig. 8' with the holder shaft axis inclined slightly (herein at an angle of 5) with respect to the Vertical. The screws 45 may thereafter be tightened to clamp the parts firmly in position. It will be understood prior to the grinding operation that the work holder may be inv its raised position and, if, desired, the work holder may be in the. position shown in Fig. 9 with the friction clutch held released by the roller 65 with the pulley 54. The bit may then be attached to the work holder shaft. The motor 48 may then be started and upon lowering of the workholder along the vertical guides, th friction clutch is automatically applied bythe coil spring, thereby connecting the work holder to the shaft of the motor so that the drill bit is rapidly rotated. The-operator may then grasp the lever 22 to manipulatethe latter, thereby to movethe work holder laterally, along the horizontal guides to bring the drill bit into operative relation with the grinding wheel, As the drill bit is rapidly rotated with the work holder shaft, the operator may-manipulate the hand wheel 28 to effect, through the chain and sprocket connections 26, 29, 30, movement of th drill bit in a rectilinear path tangentially with respect to the grinding wheel periphery, thereby properly to grind the slightlyinclined forward tapered surface I I of the drill bit to determine the proper bit gauge. The counterweight it!v facilitates raising of the work holder and crosshead vertically along the vertlcalguides. I y

The pulley 52 may be adjusted relative to the motor shaft simplyby loosening the nut 51 and swinging the pulley about the motor shaft axis, thereby to vary the tension of the driving belt. When the work holder is, in its raised position; that is, when it reaches its limit of vertical travel along the vertical guides, the roller 65 engaging the upper surface of the pulley 54 holds the clutch member 62 out of engagement with the clutch member 6| so that drive of the work holder shaft is interrupted. 1 As the periphery of the grinding wheel engages the work duringthe grinding operation, itevenly wears away, and by moving th work piece in a rectilinear path tangentially with respectto the wheel periphery, the wheel wear is evenly distributed over the wheel periphery between the side surfaces of the wheel. For instance, after grinding small diameter bits, as indicated at A in Fig. 11, larger diameter bits B may be placed against the wheel so the wheel periphery which was worn sharply concaved, is worn away at the sides. By grinding different size drill bits, the wheel wear is therefore evenly distributed over theface of the wheel so that the need of special dressing tools for the wheel is eliminated, This greatly increases the effective life of the wheel and decreases the grinding cost. v H I Instead of the hand lever 22 and the, hand wheel 28, power devices may be employed to eiTect the movements ofthe work with respect to the grinding wheel in an obvious manner. Under certain conditions the counterweight 40 and its associated chain and sprocket connections 34, 35, 38 may be omitted, thus eliminating the need of the standard 38. Such counterweight would obviously be unnecessary if a power feed is pro: vided in lieu of the hand wheel. ,Under some circumstances, a'cylindric surface may beground on a work piece, instead of the frusto-conical surface, disclosed, and at that time, the work holder wouldbe adjusted into its vertical position shownin Fig. 4. Also work pieces other than drill bits may be ground by the improved apparatus. Other modes of operation and advantages of the invention will be clearly apparent to those skilled in the art.

While there is in this application specifically described one form which the invention may assume in practice, it will be understood that this form of the same is shown for purposes of illustration and that the invention may be modified and embodied in various other forms without departing from its spirit or the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. In agrinding apparatus, a grinding wheel, means providing rectangularly related guideways, said guideways lying in planes perpendicular to planes including the axis of rotation of said wheel, a rotatable work holder mounted on said guideway-providing-means for movement along said guideways and carrying a workpiece, means for driving said work holder to rotate the workpiece about its longitudinal axis during the grinding operation, means for moving said work holder along one of said guideways to move the workpiece in generally the direction of its axis along a rectilinear path tangentially with respect to the wheel periphery, means for swivelling said work holder on an axis parallel to the axis of rotation of said wheel to incline the longitudinal axis of the workpiece with respect to its rectilinear path, and means for moving said work holder along the other guideway to move the workpiece in a direction at substantially right angles to its longitudinal axis toward and from the wheel periphery. I I

2. In a grinding apparatus, a base,'a grinding wheel, a horizontal guideway on said base, a support. movable along said guideway, a second guideway carried by said movable support and arranged at right angles to said'first guideway, a second support movable along said second guideway, a member swivelled on said second support onan axis disposed at right angles to said second guideway and parallel to the axis of rotation of said grinding wheel, a rotatable work holder journaled on said swivelled member and carrying a workpiece, means for rotating said holder to effect rotation of the workpiece about its longitudinal axis, means for moving said second support along its guideway to move the workpiece along a rectilinear path tangentially relative to the wheel periphery, said member being turnable on its swivel to incline the longitudinal axis of the workpiece with respect to its rectilinear path, and means for moving said first support along its guideway to move the workpiece substantially in a radial direction with respect to the wheel toward and from the wheel periphery.

3 In a grinding apparatus, a base, a grinding wheel, a horizontal guideway on said base, a support movablealong said guideway, a second guideway carried by said movable support and arranged at right angles to said first guideway, a second support movable along said second guideway, a rotatable work holder journaled on said second support and carrying a. workpiece, means. for. driving said holder to effect rotation of the workpiece about its longitudinal axis, means for moving said second support along its guideway tomove the workpiecealon'g a rectilinear path tangentially relative to the wheel periphery, means for moving said first support along its guideway to move the workpiece substantially in a radial direction with respect to the wheel toward and from the wheel periphery, said holder driving means including motor driven connections carried by said second support, andreleasable clutch means-movable rectilinearly with the workpiece for automatically interrupting the drive of said work holder when the workpiece is in its retracted position.

a. In a grinding apparatus, a base, a grinding wheel, a horizontal guideway on said base, a support movable along said guideway, a sedond guideway carried by said movable support and arranged at right angles to said first guideway, a second support movable along said second guideway, a member swivelled on said second support on an axis disposed at right angles to said second guideway, a rotatable work holder journaled on said swivelled member and carrying a workpiece, means for driving said holder toefiect rotation of the workpiece about its longitudinal axis, means for moving said second support along its guideway to move the workpiece along a rectilinear path tangentially relative to the wheel periphery, said member being turnable on its swivel to incline the longitudinal axis of the workpiece with respect to its rectilinear path, means for moving said first support along itsguideway to move the workpiece substantially in a radial direction with respect to the wheel toward and from the wheel periphery, said holder driving means including motor driven connections carried by said swivelled member, and releasable clutch means movable rectilinearly with said work holder for automatically interrupting rotation of the workpiece when said work holder is in'its retracted position and irrespective of the swivelled position of said work holder.

5. In a grinding apparatus, a grinding wheel, a rotatable work holder carrying a workpiece, means for driving said work holder to rotate the workpiece about its longitudinal axis during the grinding operation, means for moving said work holder to move the workpiece generally in the direction of its axis along a rectilinear path tangentially to the wheel periphery, means for swivelling said work holder on an axis parallel to the axis of wheel rotation to incline the longitudinal axis of the workpiece with respect to its rectilinear path and for maintaining said work holder in its swivelled position during aforesaid rectilinear movement of the workpiece, and means engageable by said work holder and effective irre-- spective of the swivelled position of said work holder for automatically interrupting drive of the latter when the workpiece reaches its limit of travel in one direction along aforesaid rectilinear path.

6. In a grinding apparatus, a grinding wheel, a rotatable work holder carrying a workpiece, means for driving said Work holder to rotate the workpiece about its longitudinal axis during the grinding operation, means for moving said work holder to move the workpiece generally in the direction of its axis along a rectilinearpath tangentially to the wheel periphery, said driving means for said work holder including a clutch movable translationallywith said work holder during aforesaid movement of said workpieceand through which said work holder is driven, and means comprising an abutment whichremains stationary during aforesaid movement of said 8 work homer and withwhichan element of said clutch is engageable for automatically effecting release of said clutch to interrupt rotation of-sai'd work holder whenthe workpiece reaches ltsli'mit of travel in one-direction along aforesaid rectilinear path.

7. In agrinding-apparatusa base, agrinding wheel, a horizontal guideway on said base, a support movable along said guideway, a second guideway carried by said movable support and arranged atright angles to said first guideway, a second support movable along said second guideway, a member-swivelled on said second support onan'axisdisposed at right angles to said second guideway and paralleltothe-axis of rotation of said grinding wheel, a rotatable work holder journaled on said swivelled member and carryinga. workpiece, meansnfor driving said'holder to efiectretatlon ofv the workpiece aboutits'lon'gitudlnalaxis, means for moving said second support along its guideway-to move the'workpiece alcnga rectilinear path tangentially relative to the. wheel periphery, said member being turnable on its swivel to incline the longitudinal axis of the workpiece with-respect to itsrectilinear path, means for moving said first support along its guideway' tomove the workpiece substantially in a radial direction with respect to the wheel towardand'from the wheel periphery, said holder driving meansv including motor driven connections carried. by said swivelled member, and means; movable. rectilinearly with said workholder for automatically" interrupting rotation of the workpiece when: said work? holder is in its-retracted position.

8. In a grinding apparatus,a grinding wheel, a. rotatable work holder carrying a workpiece, means forrdriving said work holder to rotate the workpiece aboutv its longitudinal axis during the grinding-operation, means for moving said work holder'to move the workpiece along a rectilinear path tangentiallyof the wheel periphery, means for swivelling saidworkholder on an axis parallel to the axis of rotation of said wheel to incline the longitudinal axis of the workpiece with respect to its rectilinear path, means for moving said work holder to move the workpiece in a direction at substantially right angles to its longitudinalaxis toward and from the wheel periphery, and means for automatically interrupting drive of said work holder when the workpiece is in retracted position, said interrupting means being eiiectlve to interrupt" drive of saidwork holder irrespective of the swivelled position of said work holder.

9-. In a grindingapparatus,;a grindin wheel, a rotatable work holder carrying a workpiece, means for driving said work holder to rotate the workpiece about its longitudinal axis during the grindingoperation, means for movingsaid work' holder to movethe workpiece generally in the direction of its axisv along'a rectilinear path tangentially of the wheel periphery, means for swivelling said work holder on an axis parallel to'the axis-ofrotation of said wheel to inclinethe longitudinal axis-of the workpiece with respect to its rectilinear path, means for 'moving'said. work holder to move the workpiece in a direction at substantially right'angles to its longitudinal axis towardandfromthe wheel periphery, and means including a clutchmovabletranslationally with said work holder and arelatively stationary stop with which an element of saidclutch is' engageable for-automaticallyinterrupting drive of said work holder 'whenthe workpiece is in retracted position, said clutch being engageable with said stop irrespective of the swivelled position of said Work hoder.

JOHN C. CURTIS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Marsh Dec. 7, 1869 Penney Aug. 3, 1880 Bradley Jan. 20, 1891 Gilson Oct. 27, 1908 Number Number Certificate of Correction Patent N 0. 2,448,019.

August 31, 1948. JOHN C. CURTIS It is hereby certified that, error appears in t numbered patent requiring correction as follows:

Column 6, line 30, claim 1, strike out the generally in;

and that the said Letters Patent should be this correction therein that the same may conform to the record of the case in the Pa Ofii e.

Signed and sealed this 1st day of March, A D. 1949.

THOMAS F. MURPHY,

Assistant Uommz'ssz'oner of Patents. 

